PNNL

Abstract

The degradation of recalcitrant, abundant, naturally occurring compounds such as lignocellulose is a significant component of the global C cycle. Identifying land uses that maximize the storage of this C rather than its mineralization to CO2 will aid in recommendations to offset C emissions. Furthermore, identifying simple relationships that predict which soils are most likely to store more C will aid in C management. We compared lignocellulose degradation over 8 months in contrasting soils from each of five sites across the United States. The soils were collected from a tallgrass prairie restoration (farmland, and plots restored in 1993 and 1979), the semiarid shrub-steppe (cool, moist upper slope and warm, dry lower slope soils), long-term farmland (no-till and conventional-till), and from two forest soils (loblolly pine and Douglas fir; fertilized and non-fertilized). Soils that rapidly metabolized freshly added C exploited endogenous and newly transformed C to a lesser degree over the course of the incubation (lower slope shrub-steppe, non-fertilized Douglas fir, and tallgrass prairie farmed and 1993 restorations). We also pooled the data to find a strong relationship between sand content and lignocellulose-C remaining in the soil after 8 months (R = 0.68) and also between short-term storage of lignocellulose-C (at 7 d) and lignocellulose-C remaining after 8 months (R= 0.94). To predict C storage, models of C and soil properties must be modified to reflect microbial communities. Communities in richer soils may be more competent to use native C following fresh C additions when compared with communities in poorer soils.